Traditionally, leavened dough is prepared by adding live yeast (baker's yeast) to the dough and by proofing the dough prior to baking. Proofing usually refers to a process by which pieces of yeast dough shaped to form bakery products are raised or enlarged preparatory to their being baked. Thus pastries, rolls, breads and other bakery products must undergo proofing before being put in an oven to be baked. When dough intermixed with live yeast is placed in a warm moist environment, carbon dioxide is internally generated throughout the body of the dough to create myriad gas pockets. These gas pockets enlarge or raise the dough and also alter its texture.
When the proofed dough is baked, the resultant product is lighter and less chewy than dough products which are not raised prior to baking. Thus croissants, doughnuts, pan pizzas, rolls and breads must be properly proofed before being baked. Proofing therefore is the process by which the shaped yeast dough pieces are subjected to a moist, hot-air environment to raise the pieces, and a proofing cabinet is a chamber in which proofing takes place.
The atmosphere in which proofing of yeast dough takes place within a cabinet needs to be controlled carefully to avoid underproofing or overproofing. Should the dough pieces receive excessive heat, they will rise too fast, thereby producing large gas pockets that cause the pieces to collapse during baking. On the other hand, insufficient heat results in dough pieces that are not fully raised, and when these pieces are baked they will have an undesirably dense structure. Excessive moisture in proofing causes the product to have a mushy surface, while insufficient moisture renders the surface of the baked product tough and rubbery.
Properly proofed yeast dough pieces must be handled with great care as they are very vulnerable. Fully proofed yeast dough will quickly collapse due to overproofing. Overproofing results from the continued activity of the live yeast, resulting in excessive carbon dioxide production and weakening of the dough structure. In order to avoid the occurrence of overproofing proofed yeast dough pieces have to be baked shortly after proofing or they have to be stored under refrigerated conditions until baking.
Overproofing is particularly difficult to avoid in yeast leavened dough containing added sugars such as sucrose, glucose and/or fructose, as these sugars provide an excellent nutrient source as well as a carbon source for the production of carbon dioxide.
The use of non-fermentable sugar alcohols in bakery applications is known in the art. WO 02/26044, for instance, describes liquid bread improving compositions comprising one or more enzymes, ascorbic acid and one or more polyols (including sorbitol). It is observed in WO 02/26044 that, when present in high amounts in aqueous solutions, polyols lower the water activity to such an extent that processes which inactivate enzymes and degrade ascorbic acid and microbial infections are slowed down. This is said to be of particular advantage for the liquid bread improving compositions described in the international patent application as these ideally need a long shelf life (up to 6 months).
US 2005/0112272 describes functional bulking agents for use in baked goods, the bulking agent comprising:
at least one starch hydrolysis product which is indigestible or resistant to digestion;
at least on bulk sweetener (e.g. sugar alcohol); and
at least one emulsifying agent.
Table 1 of US 2005/0112272 describes dry mixes for baked products comprising sorbitol (14.2-33 wt. %) as well as baking powder (1.5 wt. %) and emulsifier (4.6-4.7 wt. %). The bulking agents described in the US patent application serve as a direct, one-to-one, replacement of sugar in baked products. In particular, the bulking agent is said to be very useful in the preparation of a sugar-free sponge cake.
The use of non-fermentable sugars in bakery applications is described in, for example, EP-A 0 919 131. Example 1 of this European patent application describes a granular baking product containing, amongst other things, dextrose, lactose, baking powder, emulsifier, ascorbic acid and enzyme (amylase and xylanase). In the application lactose is mentioned together with saccharose, glucose, fructose, dextrin, maltodextrin and sugar alcohols as an example of a carbohydrates that can be included in the granular baking products described therein.
U.S. Pat. No. 4,233,321 describes the preparation of white bread by combining all dry ingredients (flour, emulsifier, salt, non fat dry milk, sucrose, shortening and lactose), dissolving yeast in water, adding the yeast slurry to the dry ingredients, mixing, fermenting, dividing and rounding, proofing, moulding, proofing and baking. In the US patent it is stated that lactose is used to replace sugar and fat in dough formulations to obtain white pan bread and rolls characterised by significantly improved tenderness or “freshness” as represented by shelf lives at least 50 to 100% longer than normally obtained with the standard formulations.